Have you ever watched any Indy(independent) movies? That’s what this looks like to me.
Sure I have. I think I know what you mean -- the plot doesn't fit the normal movie formula. The characters act in strange, even contradictory ways. The teacher is held prisoner. She wants to control the kids but she knows if she shows fear or aggression it will be worse. The best she can hope for is for the period to end. She keeps mumbling about "security" but nobody is willing to help, and she won't (or can't, because of fear or school policy) leave the classroom. She's trapped.
The only way it could be worse is if the teacher were white.